In many surgical procedures, it is often necessary to ligate a plurality of vessels within the surgical site. The vessels may be severed downstream of the ligated portion. In some instances, the vessel may be ligated at two spaced apart areas and the portion of the vessel between the ligation removed. A primary reason for ligating vessels is to maintain the surgical site free from an excess of blood and to reduce blood loss in the patient. Also in certain surgical procedures wherein tumors or parts of organs and the like are to be removed, the tumor or organ may have to be separated from certain vessels. Before separating the vessels are ligated. Once a blood vessel is completely shut off, hemostasis, that is, the natural closing of the ligated end of the vessel so as to stop blood flow, will occur in several days depending on the vessel. The body, in the meantime, will continue to allow blood flow around the ligated area through appropriate capillaries and secondary vessels with the natural physiological function of the body enlarging these by-pass vessels until adequate blood flow is obtained. Hence, when ligating the vessel, there should be positive stopping of the blood flow in the main vessel; that is, no leakage which might cause blood loss in the patient and may also disrupt the natural hemostasis and concurrent manufacture of new paths of blood flow in the patient.
In the past, this closing of the vessel was usually accomplished using ligatures; i.e., threads or filaments which the doctor tied around the vessel desired to be closed. This is a time consuming process and one wherein positive closure of the vessel is not always accomplished. In recent years, hemostatic clips have replaced ligatures in many surgical procedures to close blood vessels and other fluid ducts. Very often these hemostatic clips are narrow U or V shaped strips formed of tantalum or stainless steel which are capable of being deformed and possess sufficient strength to retain the deformation when clamped about a blood vessel.
In co-pending commonly assigned patent application, Ser. No. 276,131 filed June 22, 1981 and Ser. No. 282,461 filed July 31, 1981 there are disclosed hemostatic clips made from bio-compatible polymeric materials which are absorbable or non-absorbable in body tissue. These clips comprise a pair of leg members connected at their proximal ends by a resilient hinge section and terminating at their distal ends in a locking latch means. The distal end of one of the leg members comprises a deflectable hook section. The distal end of the other leg member is configured to be engaged by the hook section when the leg members are pivoted about the hinge to close the clip about a blood vessel. These clips as described have been found satisfactory for ligating most blood vessels. However, in certain instances if the vessel is large and the pressure in the vessel great, the clips may fail. The failure usually occurs at the latch or hook section. In certain instances, sufficient pressure is placed between the vessel clamping surfaces of the legs of the clip that the hook section will deflect allowing the opposite leg to spring out from underneath the hook member and the clip open.